Weather Service Report


782 
FXUS66 KPQR 241641
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
939 AM PDT Wed May 24 2017

.SYNOPSIS...An upper level trough will continue to carve out over
Washington and Oregon today. The upper trough will linger through
Thursday with a slim threat of late day thunderstorms over the higher
North Oregon and South Washington Cascades. High pressure will
return Friday for drier, sunnier, and warmer weather. Warm and dry
conditions continue through the holiday weekend though a few late day
thunderstorms may be possible again over the Cascades early next
week. 
&&

.SHORT TERM...Today through Friday...Minimal changes to the current
forecast. A classic dry cold front moved through the area yesterday
evening and last night. This is evident in morning water vapor
imagery with a nice, large dry slot spreading through the south half
of Washington and Northern Oregon. Upper low near far SE British
Columbia as of 15Z with a trough axis extending west to southwest
through Western Washington and NW Oregon. Marine layer covers SW
Washington and NW Oregon to a line from about KUAO to KONP. 

An upper trough will continue to carve out over Washington and Oregon
today. Inland max temps today to be around 20 degrees cooler than
yesterday. KLGX doppler radar indicates some weak returns over SW WA
this morning. Think there will be a slim threat of weak showers north
of about KSLE as a disturbance drops down into the upper trough. This
reinforces the clouds through the day today.

The main upper trough will linger Thursday, with the models continue
to indicate that some backdoor convection possible over the higher N
Oregon and S Washington Cascades Thursday afternoon and evening as
moisture and instability on the back side of the upper trough moves
through. GFS and NAM, especially NAM model sounding for a point in
the N Oregon Cascades, show minimal convective threat. Opted to trim
the thunder threat a little more north and keep it out of the
Columbia Gorge. GFS indicates 850 mb temps warm about 5-8 deg C Thu,
which should result in mid to upper 70s inland. NAM suggests much
less low cloud cover Fri morning as the 975 mb flow veers more N to
NE. Believe any morning stratus will be brief, with 850 mb temps
warming another 4-5C, for inland highs getting into the lower to mid
80s. Weishaar

.LONG TERM...Friday night through Tuesday. The models continue a
decent amount of agreement with a fairly strong upper ridge over the
Pacific Northwest this weekend that begins to edge slowly eastward
early next week. The models show some indications of convection over
the higher Cascades in the late afternoon and evenings beginning late
Sunday. The threat of late day convection continues through early
next week over the Cascades. Have lowered temps some around Tuesday
and Wednesday as the models show southwest flow aloft will lead to a
developing marine layer near the coast that will begin spreading
inland. Tolleson
&&

.AVIATION...Coastal stratus will bring gradually lowering MVFR 
Cigs for most of the next 24 hours. Stratus backbuilding from 
the Cascades will bring Cigs mainly 030-050, although there may a
period this evening where clouds scatter out.

KPDX AND APPROACHES...VFR conditions with Cigs 035-045 impacting
visual approaches at times for the next few hours. Little change
until around 11z when cigs fall to 025-030 through 25/18z. /JBonk

&&

.MARINE...Pattern continues with high pressure over the NE
Pacific and low pressure inland combining to continue SCA wind 
gusts through early Thursday. Will first see winds within 10 nm 
of the Coast drop below SCA criteria later tonight, and then 
across the entire waters Thursday morning. Benign conditions look
to reign Thursday afternoon through this weekend as the pressure
gradient remains relatively week across the waters. 

Steep seas continue at 8-10 ft with dominant wave periods around
7 to 9 seconds. Expect seas to back down a bit this morning 
before building back up near 10 ft this evening. Extended the SCA
for Seas as short periods under wind wave driven/fresh swell
conditions dominate. Longer period seas will start prevailing
Thursday as the winds ease with little threat of notable winds or
seas affecting the waters until perhaps early next week. /JBonk

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 8 AM PDT Thursday for 
     Waters from Cape Shoalwater WA to Florence OR from 10 to 
     60 nm.

     Small Craft Advisory for hazardous seas until 5 AM PDT Thursday 
     for Coastal Waters from Cape Shoalwater WA to Florence OR 
     out 60 nm.

     Small Craft Advisory for winds until 2 AM PDT Thursday for 
     Coastal Waters from Cape Shoalwater WA to Florence OR out 
     10 nm.

&&

$$

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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.

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Western Regional Climate Center, wrcc@dri.edu